NRC launches inspection at Watts Bar NPP

10 May 2018

The Nuclear Regulatory Commission has launched a special inspection into the circumstances surrounding voids in the residual heat removal system, which made it inoperable for a time on both Unit 1 and Unit 2 at the Watts Bar nuclear plant.

Source: Wikimedia Commons

The residual heat removal system is used to complete the plant’s cooldown process at lower pressures and also provides important functions during certain accident scenarios. On April 19, TVA informed the NRC that calculation revisions had reduced the acceptable size of a void due to gases in the system. On April 21, the accumulated gas in the Unit 1 system was found to have exceeded the acceptable value, and on April 22, the same observation was made on Unit 2.

The NRC inspectors will review the sequence of events, drawings, calculations and acceptance criteria, walk down portions of the plant’s systems, evaluate TVA’s response and assess the adequacy of actions to address the causes of the issues.